https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciac501/6611845

Hospitalized patients with severe COVID-19 during the Omicron wave benefited from a 4th vaccine shot--Israeli study

Waning vaccine-immunity and an increased incidence of COVID-19 during the Omicron outbreak led the Israeli Ministry of Health to recommend a fourth dose of BNT162b2 for high-risk individuals. This study assessed the effect of that dose for hospitalized patients with severe/critical, breakthrough COVID-19. ...

Among hospitalized patients with severe/critical breakthrough COVID-19, a recent fourth dose was associated with significant protection against mechanical ventilation or death, compared to three doses.